1. Field
The present disclosure generally relates to automated machining techniques, and deals more particularly with a method of optimizing toolpaths used by automatically controlled cutting tools.
2. Background
CAD/CAM (computer aided design/computer aided manufacturing) systems may be integrated with CNC (computer numerically controlled) systems to provide rapid, efficient machining of workpieces. CAM systems use various toolpath strategies to guide a cutting tool during rough machining operations in which the workpiece is machined to near net-shape. In one toolpath strategy, commonly referred to as constant-offset or parallel-offset, the degree of radial engagement of the cutting tool with the workpiece varies as the cutting tool moves along the toolpath. While the material removal rate (MRR) may be optimized along straight cuts, the feed rate must be reduced when the tool enters sharp curves or corners where the radial engagement increases.
In order to increase machining efficiency and reduce tool wear/breakage, adaptive type toolpath strategies have been developed in which full radial engagement of the cutting tool with the workpiece is maintained substantially throughout the rough machining operation. Based on full radial engagement of the cutting tool, the CAM system may calculate an axial cutting depth and feed rate that result in higher utilization of the available machine tool power. Although adaptive toolpath strategies may significantly increase cutting efficiency, the machine utilization rate is still not fully optimized. This is because, while a toolpath program may call for constant cutting tool feed rate, the machine may not be able to actually achieve a constant feed rate due to its inertial mass. For example, when the cutting tool reaches an outer cut area boundary, the machine is required to decelerate, stop, reverse direction and re-accelerate. The loss of efficiency due to these frequent changes in toolpath velocity and direction may be particularly severe along narrow or tight regions of a workpiece. In these regions, numerous, short back-and-forth passes of the cutting tool are necessary, each of which requires the cutting tool to decelerate, change direction and reaccelerate.
Accordingly, there is a need for a method of rough machining a workpiece using an adaptive toolpath strategy that increases machining efficiency, particularly along narrow or tight regions of an area being machined. There is also a need for a machining method that maintains the feed rate of a cutting tool at a substantially constant velocity while the cutting tool remains in substantially full engagement with the workpiece.